This application addresses key aspects of the research team's long range goals to identify and characterize factors critical to in vitro oocyte maturation (IVM) and fertilization (IVF), and the early development of mammalian embryos. Cattle and rabbits have been selected as experimental models because they are excellent species for comparative studies and are consistent with superb university facilities available for this project. Oocytes from ovaries of calves and slaughterhouse cattle, and embryos subsequently derived from these studies in vitro as well as in vivo following superovulation of cattle and rabbits, will provide a rich source of experimental material to complete the experiments described. Under the first three specific aims, regulation of events necessary for acquisition of full meiotic competence and maturation of bovine oocytes will be determined for oocytes from (1) pre-antral follicles in comparison with those from (2) small and (3) larger antral follicles. Expertise in follicular growth and differentiation, IVM and IVF will be combined to establish molecular components and other culture conditions required for optimal recovery of follicular oocytes which will support a high rate of IVM, IVF, cleavage and subsequent normal embryo development following transfer. Logically following are specific aims (4) and (5) which focus on molecular mechanisms that regulate the development of bovine and rabbit embryos cultured in defined media recently developed by this group. These novel studies provide a unique opportunity to establish conditions required for in vitro development of completely competent embryos. The expected outcome is a substantial increase in knowledge of essential regulatory elements in vitro that control growth and maturation of oocytes, fertilization and the production of viable mammalian embryos. This information can be applied to developing IVM, IVF and embryo culture procedures which can be used to address fundamental questions in development and for the production of live young from domestic and wildlife species of special concern.